Many businesses are providing access to their products and services through applications that are delivered over computer networks such as the Internet. These applications typically have a multi-tiered architecture. In those cases where the applications are delivered over the Internet they are commonly referred to as Web applications. FIG. 1 is a block diagram of a Web application 100 having a multi-tiered architecture.
Web application 100 includes client layer 110, application layer 120, and database layer 130. Client layer 110 includes user interface 112 that runs on a client computing device such as a desktop computer, a laptop computer, a personal digital assistant, a telephone, and the like. In a Web-based environment, user interface 112 is typically a Web browser. User interface 112 may collect input from a user and provide that input to application layer 120 for processing.
Application layer 120 includes application server 122 to receive and process input from client layer 110. Application server 122 typically includes a number of subcomponents including, for example, connectivity layer 140, presentation logic 142, business logic 144, and database interface 146. Connectivity layer 140 provides connections to client layer 110 using protocols such as the HyperText Transfer Protocol (HTTP). The HTTP protocol refers to any of the HTTP protocols including, for example, the protocol described in Request For Comments (RFC) 2616 entitled, “HyperText Transport Protocol—HTTP/1.1,” June 1999 (hereinafter, the HTTP protocol). Presentation logic 142 generates a Graphical User Interface (GUI) using, for example, a markup language such as the Hyper Text Markup Language (HTML). Business logic 144 represents the core of the application, for example, the rules governing the underlying business process (or other functionality) provided by the application. Database interface layer 146 provides an interface to database layer 130. The Java 2 Enterprise Edition Specification v1.3, published on Jul. 27, 2001 (the J2EE Standard) defines an increasingly popular architecture for application layer 120.
Database layer 130 includes data access logic used by business logic 144 to store and retrieve data in database 132. Database 132 provides non-volatile storage (sometimes referred to as a persistent store) for the data accessed and/or processed by application layer 120. Database 132 may be, for example, a relational database or an object-oriented database.
In a Web-based environment, presentation logic 142 may be provided by a Web component such as a servlet. A servlet refers to a server-side Web component that interacts with a client through a request/response protocol. For example, the servlet may receive a request message, perform some processing, and return a response message to the client. A servlet processes a request message using a service method. Typically, the request/response messages are implemented according to one of the HTTP protocols.
In conventional Web applications, the connection to a client is automatically closed when the servlet exits its service method and the response message is sent to the client. Also, conventional Web applications release the message processing resources (e.g., finalize request/response objects) after the response message is sent to the client. Thus, in conventional Web applications, the client is no longer accessible after the response message is sent.